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End-of-Pipe Treatment Techniques
Published in Guttila Yugantha Jayasinghe, Shehani Sharadha Maheepala, Prabuddhi Chathurika Wijekoon, Green Productivity and Cleaner Production, 2020
Guttila Yugantha Jayasinghe, Shehani Sharadha Maheepala, Prabuddhi Chathurika Wijekoon
A wet scrubber is a device used to control air pollution by removing particulate matter (PM) and acidic gases that are present in a carrier gas stream. The device uses a liquid, typically water or a water-based solution, to capture the pollutants. The basic processes of impaction, diffusion, interception, and/or absorption are applied in the process of removing the pollutant. The gas stream that is then emitted from the scrubber no longer contains high residual amount of the pollutants and poses no threat of pollution. Pollutant-containing liquid is collected for disposal, undertaking further treatment if required as shown in Figure 4.2. There are numerous types of wet scrubbers that remove both acidic gas and PM (Schifftner and Hesketh, 1996).
Control of Particulate Emissions
Published in Jeff Kuo, Air Pollution Control Engineering for Environmental Engineers, 2018
For any wet scrubber, the liquid flow rate is important to its removal performance. The rate of liquid flow is often expressed in terms of the liquid-to-gas ratio. Most wet scrubber systems for particulate removal operate with liquid-to-gas ratios between 4 to 20 gal/1,000 actual cubic feet; that is equivalent to a dimensionless ratio of about 0.0005 to 0.0025. Higher ratios do not usually enhance performance. Instead, they may exert a slight adverse impact due to changes in size distribution of the droplets. On the other hand, low liquid-to-gas ratios can have a severe adverse impact because of insufficient collection targets present.
Industrial Odor Control
Published in Paul N. Cheremisinoff, Air Pollution Control and Design for Industry, 2018
First cost and operational costs should both be considered when selecting equipment. Actual field tests have shown that the most effective means of odor reduction is incineration and multiple-step wet scrubbing. With the high costs and limited supply of fuels, multiple-step wet scrubbing is emerging as the most economical solution. Selection of the type of wet scrubber used should be based on the nature of the odorous constituents and physical nature of the exhaust stream.
A concept and industrial testing of a superheated steam rotary dryer demonstrator: Cocurrent-triple pass design
Published in Drying Technology, 2019
Y. Chryat, M. Esteban-Decloux, C. Labarde, H. Romdhana
The partially desuperheated steam is recycled by a SHS-blower, superheated by a heat exchanger and then supplied to the inlet of the dryer. The removed vapor from the product is supplied to a cooling unit for energy recovery. A wet scrubber is used to clean the exhaust vapor by spraying water. The use of water also leads to cooling down the SHS up to the saturation state. The saturated steam is then condensed. The non-condensable gases (e.g., air, VOC) are removed and burned off. The vapor can be superheated up to 600°C with combustion gases produced by a natural gas burner (22–110 kW). The combustion furnace (3 m length, 1 m diameter) is made of steel covered with refractory concrete. The superheater consists of series of 6 shell-and-tube exchangers. The first two series consist of 50 tubes each (21.3 mm diameter, 1 m length). The last 4 series consist of 28 tubes each (26.9 mm diameter, 1 m length). Within each tube series, the SHS flows through a set of tubes and exchanges heat with the combustion gases flowing outside the tubes in cross flow. The outlet combustion gas is finally used in a heat recovery exchanger to preheat the primary combustion air.
Evaluating removal of tar contents in syngas produced from downdraft biomass gasification system
Published in International Journal of Green Energy, 2018
Muhammad Awais, Wei Li, Arfan Arshad, Zeeshan Haydar, Nauman Yaqoob, Sajjad Hussain
Producer gas released from the outlet of cyclone separator was used as input in wet scrubber to reduce further tar in gas. The final value of tar was measured at the outlet of wet scrubber. It was seen that average value of tar content was reduced from 1,827 to 676 mg/m3 when wood chip was used as feedstock, while in case of corn cubs its value was reduced to 2,582 to 1,048 mg/m3. Percentage reduction of tar contents for wood chips and corn cobs was 63% and 59%, respectively. The results revealed that wet scrubber removes a large amount of tar when we used wood chips as fuel than corn cobs. Some previous have shown that water-based scrubber could remove tar contents up to 62%, and if these are equipped with oil-based scrubber they could remove tar contents up to 99% (Rameshkumar and Mayilsamy 2012; Zwart 2009). Wet scrubber can also remove the metals and dust particles which remains in the gas phase (Stevens 2001).
Biomass gasifier – internal combustion engine system: review of literature
Published in International Journal of Sustainable Engineering, 2021
A. A. P. Susastriawan, Yuli Purwanto
The producer gas is passed through the scrubbing material. Depending on scrubbing material, scrubber can be categorised as wet and dry scrubber as shown in Figure 4. In wet scrubber, liquids is used as scrubbing material. On the other hand, solid material is used as scrubbing material in dry scrubber. Further, wet scrubber can be approached with impinging, spray, and venturi scrubber. Figure 5 shows schematic diagram of flow configuration between producer gas and liquid in impinging, spray, and venturi scrubber. Producer gas is impinged to the scrubbing liquid in the vessel. Tar condenses when contact with the liquid and adsorbed by the liquid. In spray scrubber, producer gas flows upward and liquid is spread in an opposite direction. The spray scrubber requires pump to generate the spray. Meanwhile, producer gas is injected into the scrubbing liquid stream in venturi scrubber. In other to enhance adsorption surface area, microbubble venturi scrubber has been developed and tested (Unyaphan et al. 2017a, 2017b). The scrubbing liquids have been use are water (Phuphuakrat, Namioka, and Yoshikawa 2011; Bhave, Vyas, and Patel 2008), waste palm oil (Ahmad and Zainal 2016), vegetable oil (Unyaphan et al. 2017a; Phuphuakrat, Namioka, and Yoshikawa 2011), diesel fuel, biodiesel fuel and engine oil (Unyaphan et al. 2017a). The type of scrubbing material has a significant effect on adsorption efficiency. According to Phuphuakrat, Namioka, and Yoshikawa (2011), the adsorption efficiency can be ranked from the highest to the lowest such that diesel fuel, vegetable oil, biodiesel fuel, engine oil and water. Meanwhile, various solid materials have been used as adsorbent of dry scrubber, such as chestnut wood char (Paethanom et al. 2013) and bio-char (Shen et al. 2016).